Nanotube diode reverses itself

October 6/13, 2004

Researchers from GE Global Research Center
have constructed from a single carbon nanotube a device that restricts
the flow of electricity to a single direction and can electrically switch
from one direction to the other.

Carbon nanotubes are rolled-up sheets of carbon atoms that can
be narrower than a nanometer. A nanometer is one millionth of a milliliter,
or the span of 10 hydrogen atoms.

This minuscule p-n junction diode could be used as a field-effect
transistor or a light-emitting diode. The device is a step forward in
the push to make nanoscale electronic components, which promise to be
faster and lower-power than today's larger versions.

The device is made from a single-walled nanotube connected to
electrodes at either end and with gate electrodes positioned beneath either
end. Sending positive current to a gate electrode creates a positive electric
field around a portion of the nanotube, making that area of the tube draw
negatively charged current from the far contact electrode.

Electronic components are usually modified using chemicals rather
than an electrical field; the chemical method is difficult to do with
carbon nanotubes, according to the researchers.

Discrete electronic or sensor components made from the nanotube
devices could be used practically within a few years, but it is likely
to be a decade or more before nanotube devices can be used for electronic
applications that require millions of interconnected components, according
to the researchers. The work appeared in the July 5, 2004 issue of Applied
Physics Letters.